The invention relates generally to a full-face (ie. nose and mouth) mask and to a cushion therefor, for example, for use in the treatment of respiratory conditions and in assisted respiration.
Full-face masks are commonly used in the treatment of respiratory conditions and sleep disorders (e.g., obstructive sleep apnea) by delivering a flow of breathable gas for, or to assist, patient respiration. These masks typically receive a gas supply line which delivers gas into a chamber formed by walls of the mask. The walls usually are semi-rigid and have a face contacting portion including an aperture which is generally aligned with the wearer""s nostrils and mouth. The face contacting portion can comprise a soft, resilient elastomeric material which may conform to various facial contours. The mask normally is secured to the wearer""s head by straps. The straps are adjusted to pull the mask against the face with sufficient force to achieve a gas tight seal between the mask and the wearer""s face. Gas is thus delivered to the mask and through the aperture to the wearer""s nasal passages and throat.
Problems often arise with masks of the above configuration. For example, the mask may be dislodged, thereby breaking the seal between the mask and wearer. This may occur if the wearer rolls over when sleeping thereby creating a drag force on the gas supply line which is transmitted to the mask, breaking the seal. In the case of a mask being used for the administration of Continuous Positive Airway Pressure (CPAP) treatment for the condition obstructive sleep apnea, such a leak can result in the pressure supplied to the entrance of the wearer""s airway being below the therapeutic value, and the treatment becoming ineffective.
Another problem is that the face contacting portion may apply excessive pressure to the wearer""s face resulting in discomfort and possibly skin irritation. This can occur because the face contacting portion has to distort beyond its normal range of elasticity to conform to certain facial contours which requires the application of excessive forces. In some cases these excessive pressures and forces may cause the face to distort to conform with the face contacting portion to increase wearer discomfort, facial soreness and ulceration.
It is an object of the invention to overcome or at least substantially ameliorate one or more of the foregoing disadvantages.
In one broad form, the invention discloses a full-face mask cushion to sealingly connect a mask to a wearer""s face, the cushion comprising:
a nasal bridge region, a cheek region and a chin region;
a first membrane comprising a substantially triangularly-shaped frame of resilient material having a first molded inwardly curved rim;
a second membrane of resilient material, said second membrane being thinner than said first membrane, said second membrane having a second molded inwardly curved rim, said second membrane curved rim spaced a first distance from said first membrane curved rim in said cheek region and said second membrane curved rim spaced a second distance from said first membrane curved rim in said nasal bridge region, said second distance greater than said first distance, said distances measured when the mask is not in use, a portion of said second membrane curved rim forming a face contacting seal.
Preferably, the rim and seal portion are shaped to generally match facial contours of the facial tissue around the sides and over the bridge of the nose and between the bottom lip and the chin.
In one particularly advantageous form, the membrane is substantially saddle-shaped. The membrane further has a centrally located aperture through which the wearer""s nose and mouth pass to enter said cavity.
It is preferred that the cushion and membrane each include a co-located notch to accommodate the bridge of the nose of the wearer. Typically, the seal portion contacts at least the wearer""s nose, and preferably, also the facial tissue around the sides and over the bridge of the nose and between the bottom lip and the chin.
The invention further discloses a full-face mask for connection to a wearer""s face comprising:
a mask body for connection with a supply of breathable gas; and
a full-face cushion secured to said mask body, the body and cushion forming a nose and mouth-receiving cavity, said cushion including:
a nasal bridge region, a cheek region and a chin region;
a substantially triangularly-shaped first membrane of resilient material having a first molded inwardly curved rim to surround wearer""s nose;
a second membrane also of resilient material, said second membrane being relatively more flexible than said first membrane, said second membrane having a second molded inwardly curved rim, said second molded rim being of the same general shape as said first molded rim and fixed to and extending away from said first membrane so as to have a second membrane inner surface spaced a first distance from an outer surface of said first molded rim in said cheek region and said second membrane inner surface spaced a second distance from said first membrane outer surface of said first molded rim in said nasal bridge region, said second distance greater than said first distance, said distances measured when the mask is not in use, a portion of said second molded rim forming a face contacting seal; and
wherein said seal portion is substantially coterminous with respect to said second molded rim and is resiliently deformable towards said first membrane in use of said mask.
The mask body can further include attachment points from which securing straps can be attached, and by which the mask can be secured to the wearer""s head. The nasal mask can yet further comprise an arm depending from said body from which a further securing strap(s) can be attached.
The invention further discloses a CPAP treatment apparatus comprising:
a flow generator for the supply of gas at a pressure elevated above atmospheric pressure;
a gas delivery conduit coupled to said flow generator; and
a full-face mask in turn coupled to said conduit to said nasal mask including:
a mask body for connection with a supply of breathable gas; and
a full-face cushion secured to said mask body, the body and cushion forming a nose and mouth-receiving cavity, the cushion including:
a nasal bridge region, a cheek region and a chin region;
a substantially triangularly-shaped first membrane of resilient material having a first membrane having a molded inwardly curved rim;
a second membrane having a second molded inwardly curved rim also of resilient material, said second membrane being relatively more flexible than said first membrane, and being of the same general shape as said first molded inwardly curved rim and fixed to and extending away from said first membrane so as to have an inner surface spaced a first distance from said first molded rim in said cheek region and said second membrane inner surface spaced a second distance from said first molded rim, said second distance greater than said first distance, said distances measured when the mask is not in use, a portion of said second molded rim forming a face contacting seal; and
wherein said seal portion is generally coterminous with respect to said second molded rim and is resiliently deformable towards said first membrane in use of said mask.
In one particularly preferred form, a supply of gas can be provided to said cavity, said supply of gas assisting, but not solely causing maintenance of a seal by said seal forming portion of said membrane to the face of the wearer in use of the cushion.
Advantageously, because the membrane and the rim are substantially shaped to the facial contour, and the membrane does not need to turn in on itself, as in the prior art, thus contacting the face without folds or creases. With the cushion/mask secured to the wearer""s head, the headstraps need only to be tensioned to balance the force due to mask gas pressure that tends to lift the mask off the face. Such relatively lower mask-to-face pressure results in greater patient comfort, and a reduction in the likelihood of skin irritation.